Techniques for separation of particulates are of wide applications among which one commonly seen application is to separate cells. In biomedical science, detection and quantification of cancer cells or rare cells present in body fluids are regarded as a potential indicator for clinical diagnoses, prognostication, and biomedicine research. For example, circulating tumor cells (CTC) are rare in the blood of patients with metastatic cancer, and it is possible to monitor the response of CTC to adjuvant therapy. Other examples include detections of fetal cells contained in maternal blood, cells contained in whole blood, and endothelial colony forming cells (ECFC) contained in umbilical cord blood (UCB).
Various techniques of particulates separation are now applied in the separation of cells, including fluorescence activated cell separation (FACS), dielectrophoresis (DEP) cell separation, separation techniques that employ massively parallel microfabricated sieving devices, magnetically activated cell separation (MACS), and other techniques that uses optics and acoustics. Among these cell separation techniques, FACS and MACS are most often used.
Although it is often used, FACS suffers several drawbacks, including high cost, system bulkiness, difficulty in disinfection, consuming a great amount of sample in the operation thereof, and having only limited sensitivity in the operation of detection and separation.
Contrary to FACS, MACS is efficient to obtain a major quantity of the target cells in a short period and reduces the consumption of sample. However, these cells must be transferred to a slide or an observation platform before they can be observed with a microscope. Such a process of transfer often leads to a great loss of cells.
U.S. Pat. No. 5,565,105 discloses a magnetocentrifugation method, wherein charged particles are deposited in a rotor board and a magnetic field is vertically applied to the rotor board. When the rotor board is brought into rotation, the charged particles carried by the rotor board are caused to move through the magnetic field, whereby the charged particles are subjected to Lorentz force and separated from non-charged particles.
U.S. Pat. No. 6,723,510 discloses a method for separating particles with minimized particle loss, wherein a detergent containing matrix beads is bound with a sample containing target particles in order to reduce the loss of the target particles in the separation processes.